Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
Recently, a touch panel apparatus that can be operated by touching an operation key displayed on a screen has been popular. With such a touch panel apparatus, a technique that feeds back sense of pressing the operation key to an operator by sense of touch has been known.
In the technique, vibrating devices are located in the touch panel. While the operator touches an operation surface on the touch panel, a drive signal is applied to the vibrating devices, thus the touch panel is vibrated. In the technique, to check whether the vibrating devices are damaged or not, the vibrating devices are periodically vibrated while the equipment is not used. When a piezoelectric voltage becomes equal to or less than a reference voltage, the touch panel notifies its abnormality.